1. Field of the Invention
The present invention relates to an ADF (Automatic Document Feeder) for sequentially conveying documents stacked on a feed tray while separating them one by one, and an image forming apparatus including the same.
2. Description of the Background Art
Japanese Patent Laid-Open Publication No.11-192374, for example, discloses an ADF including two receipt trays respectively assigned to a one-side mode and a both-side mode. The one-side mode and both-side mode refer to the conveyance of a document carrying an image on one side and that of a document carrying images on both sides, respectively. The two receipt trays allow documents to be sequentially driven out of the ADF in order of page while promoting rapid conveyance.
Japanese Patent Laid-Open Publication No. 8-110662 proposes an ADF also including two trays respectively assigned to the one-side mode and both-side mode. The tray for the one side mode is positioned horizontally and partly slidable. The tray for the both-side mode is positioned below a feed tray. Further, the proposed ADF includes a plurality of belts positioned on a glass platen and driven independently of each other and a reversing mechanism. The belts are driven synchronously or asynchronously to each other in accordance with the length of a document as measured in the direction of conveyance, thereby reducing a copying time when documents of different sizes are stacked together.
Japanese Patent Laid-Open Publication No. 6-242648 teaches an ADF in which a usual discharging section and a sheet-through discharging section are arranged one after the other in the direction of conveyance. In addition, a foldable document tray is positioned at the rear of the sheet-through discharging section.
Japanese Patent Laid-Open Publication No. 5-6053 proposes an ADF including a feed tray mounted on a side wall and a receipt tray positioned above a glass platen. The receipt tray forms part of a movable main frame that implements a feeding and discharging device. The main frame is movable between a closed position and an open position and lockable at a preselected angle. When the main frame including the receipt tray is opened to and locked at a preselected angle, one roller of a roller pair is released from the other roller.
Japanese Patent Laid-Open Publication No. 9-292742 discloses an ADF including a single receipt tray positioned below a feed tray and available for both of the one-side mode and both-side mode.
Japanese Patent Laid-Open Publication No. 8-91711 pertains to a sheet-through type copier including a single receipt tray positioned below a feed tray and also available for both of the one-side mode and both-side mode. A reversal path assigned to the both-side mode and a roller pair for nipping the edge of a document whose one side has been scanned are arranged in the vicinity of a scanning position.
Likewise, Japanese Patent Laid-Open Publication No. 9-6063 discloses an ADF including a single receipt tray positioned below a feed tray and shared by the one-side mode and both-side mode. This ADF does not include a switchback path for reversing, in the one-side mode, documents scanned in order to drive them out in order of page.
Further, Japanese Patent Laid-Open Publication No. 10-20568 teaches an ADF including a first receipt tray positioned below a feed tray, first conveying means for conveying a document scanned to a switchback path below the first receipt tray, second conveying means for driving the document out of the switchback path, an extendible second receipt tray mounted on the outer periphery of the ADF, and a path selector for selecting one of a plurality of paths including the switchback paths. In the usual one-side mode, documents of size A3 or similar large size are delivered to the second receipt tray. If the second receipt tray is not sufficiently extended, such documents are delivered to the first receipt tray and prevented from dropping thereby.
Laid-Open Publication Nos. 11-292374, 8-11-662, 6-242648 and 5-6053 stated above each need two receipt trays or a feed tray protruding from the side wall of the ADF. However, the two receipt trays or the protruding feed tray occupies an extra space in addition to the space of the ADF itself.
Laid-Open publication No. 9-292742 has a problem that the path at the discharging side is sophisticated and needs a great number of parts, resulting in an increase in cost. Laid-Open Publication No. 9-6063, as well as 9-292742, cannot convey the next document to the scanning position until the preceding document has been driven out to the receipt tray, obstructing rapid conveyance. Laid-Open Publication No. 8-91711 pertains to a configuration in which a document is conveyed to a glass platen and stopped there, but does not even suggest an implementation for rapid conveyance.
A problem with Laid-Open Publication No. 5-6053 is that when the movable main frame is opened for the removal of a jamming sheet, impurities including dust are apt to enter the ADF.
Laid-Open Publication No. 10-20568 gives no consideration to a configuration in which when a document scanned is driven out to the first receipt tray via the switchback path, the next document is brought to a stop on the glass platen. Further, the first and second conveying means (drive rollers) are associated with the switchback path while the second receipt tray is mounted on the outer periphery of the ADF. This obstructs small size, space saving construction.
Assume that the ADF includes a stamp unit in addition to the two receipt trays. Then, a top cover, for example, protrudes above the ADF and again obstructs small size, space saving construction.